1. Field of the Invention
The present invention relates to a fastener guide mechanism in a fastener driving tool.
2. Description of the Prior Art
A conventional fastener driving tool includes a driver guide within which a driver is reciprocally driven for driving fasteners such as nails. The fasteners are stored in a magazine and are connected in series by a carrier. The fasteners connected by the carrier are fed into the fastener guide track one after another through a fastener feeding channel formed in a fastener guide connected to the driver guide.
The carrier may be formed by various materials such as thin wires and a belt made of synthetic resin, and therefore the thickness of the carrier varies with the type of its material. For example, the carrier made of thin wires has a smaller thickness than one formed by a belt made of synthetic resin.
For the above reason, it is proposed to adjust the width of the fastener feeding channel, depending on the type of the carrier. Japanese Utility Model Publication No. 1-21732 discloses a door plate biased by a spring for changing the width of the fastener feeding channel, depending on the type of the carrier. Japanese Utility Publication No. 53-47254 and Japanese Laid-Open Utility Model Publication No. 63-197075 disclose use of a spacer for adjusting biasing force of a guide member.
However, with the former prior art mechanism, the biasing force of the spring varies with the type of the carrier of fasteners because of change of thickness. Therefore, in case that the spring is determined to have a relatively strong biasing force required for the carrier made of wires, a stronger biasing force is applied to the carrier if the fasteners have been changed to those carried by the carrier formed by a belt made of synthetic resin. This may prevent the fasteners from being smoothly fed toward the driver guide track. On the other hand, in case that the spring is determined to have a relatively small biasing force, a smaller biasing force is applied to the carrier if the fasteners have been changed to those carried by the carrier made of wires. This may cause unstable support of the fasteners, and the fasteners cannot be smoothly fed toward the driver guide track. In either of these cases, it is very difficult to determine the biasing force to an appropriate value.
Further, with the latter prior art mechanism, the biasing force can be adjusted according to change of the carrier carrying the fasteners by changing the restraining position of the guide member. However, such adjusting operation must be manually performed after the operator has recognized the kind of the fasteners or the kind of the carrier within a fastener feeding channel.